The use of antisense RNA or DNA to modulate gene expression offers a new dimension in radiation biology. Integrated into long-term projects in our laboratories, two research areas are currently in progress in which antisense technology plays a key role. The first investigates the c-raf-1 oncogene and its relationship to radiation resistance in tumors of the head and neck region. Sense and antisense constructs of this gene have already been made with 5 different vectors, and tested in mammalian cells. A major observation has been that raf hyperexpression in mouse and human cells results in tumorigenicity in nude mice, and an increased D(O) (radiation resistance) in radiation survival studies. Expression of the antisense raf results in a delay in the growth of nude mice tumors and a decreased D(O) (radiation sensitivity). The role of poly(ADP-ribose) polymerase in mammalian cellular radiation sensitivity and repair of radiation damage represents the second group of ongoing studies. A recent observation has been that inhibitors of poly(ADP-ribose) polymerase promote radiosensitization of normal and tumor cells. We have used the full-length cDNA of the polymerase and its 5' and 3' regions, in sense and antisense orientations, to construct 7 vectors with retroviral or other inducible promoters. The central objective of this proposal is the study of the molecular effects of artificial antisense genes (antisense RNA, AIM 1) or antisense oligodeoxynucleotides (antisense DNA, AIM 2) designed against selected oncogenes or radiation-related genes. Both antisense RNA and antisense DNA will be used in vitro to sensitize cells cultured from radiation-resistant human tumors. An important part of this proposal will investigate alternative ways to deliver effective doses of the response-modifying agents to the cells, with special emphasis on liposome techniques. The ultimate goal of this proposal is to extend these in vitro studies to the in vivo modification of the radiation-response, particularly in tumors which appear to be refractory to radiation therapy.